1. Technical Field
The disclosure relates generally to the transmission of audio and video signals from a server to a client.
2. Discussion of the Related Art
Conventional multimedia streaming systems typically stream a single audio stream and a single associated video stream from a source, typically called the “server”, to a destination, typically called the “client”. The combined bandwidth of the audio and video signal streams defines the required channel bandwidth between the server and the client. If this channel bandwidth is reduced because of, for example, congestion, then conventional server systems have little or no means of adequately dealing with this bandwidth reduction problem and transmission must cease. Therefore, modern multimedia server systems employ various techniques that allow a source, such as a server, to adapt to a reduction in server-client bandwidth.
One known approach to solving this problem is to make multiple alternate audio and video streams available to the server, where the alternate streams are encodings of the same content but with different bandwidths. This gives the server the option of selecting the most appropriate audio/video signal streams for transmission to the client. In a further refinement of this approach, each alternate stream can also be sub-sampled, where the server selectively transmits only parts of an alternate audio/video stream, thereby permitting more choice in adapting the audio/video stream bandwidths to the actual server/client channel capacity.
The source of the multiple alternate streams need not necessarily be a part of the same system as the server system that connects to the various clients and that performs the bandwidth adaptation. An example of such a system providing multiple alternate signal streams is shown in FIG. 1, where an encoding system 10 encodes an audio signal and or video signal each with various different bandwidths, that is, the signals are encoded at various different bit rates. The encoding system 10 sends all the alternate streams to a stream selection system 20, denoted as a server. The stream selection system selects and forwards the appropriately encoded signals, possibly sub-sampled, to each client 30-l to 30-n that is connected to or communicating with the stream selection system 20.
In a system configuration such as shown in FIG. 1, certain information must be conveyed from the encoding system 10 to the stream selection system 20, in order for the stream selection system 20, that is, the server, to know which streams it is receiving and what the selection options are.